How can solar panels power a car?

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­If there's no such thing as a free lunch, how about a free ride? Think of how wond­erful it would be if your car could continue running without you spending a dime on fuel. If you drove a solar-powered car, that auto dream would come true. Much like solar-powered homes, solar cars harness energy from the sun, converting it into electricity. That electricity then fuels the battery that runs the car's motor. Instead of using a battery, some solar cars direct the power straight to an electric motor.

Solar cars can accomplish this through photovoltaic cells (PVC). PVCs are the components in solar paneling that convert the sun's energy to electricity. They're made up of semiconductors, usually made of silicon, that absorb the light. The sunlight's energy then frees electrons in the semiconductors, creating a flow of electrons. That flow generates the electricity that powers the battery or the specialized car motor in solar cars. For more details about solar energy, read How Solar Cells Work.

Although you won't find solar cars at any dealerships, people have been building their own models since the 1970s. Ed Passerini who constructed his own completely solar powered car called the "Bluebird" in 1977 and Larry Perkins who drove the "Quiet Achiever" in 1982 both receive nods as the first people to do so. Ford and Mazda have even tested the waters with solar hybrid concept cars. The 2006 Ford Reflex installed solar panels in the headlights, and the 2005 Mazda Senku featured solar panels on its roof to help charge its battery. The 2008 Cadillac Provoq uses solar panels to power accessories, such as interior lights and the audio system.

While the Reflex, Provoq and Senku are merely concept models, cars outfitted with solar panels may be tiptoeing their way into the consumer automotive industry as companies try to find innovative methods for dodging gasoline dependence. French car company Venturi has made one of the most publicized efforts with its unveiling of the Eclectic model prototype at the 2006 Paris Auto Show. The Eclectic combines solar, wind and battery power to run a three-passenger car specifically for city driving. Solar panels cover its roof, and a wind turbine can also catch energy on blustery days. The Venturi Eclectic isn't cut for highway travel, however, since it only goes up to 30 miles per hour (48 kph).

That brings up the question of how practical solar-powered automobiles are. We'll steer toward that topic on the next page.

Are solar cars practical?

Canadian Marcelo da Luz is also trumpeting the solar car during his journey to the Arctic Circle in -- what else? -- a solar car. Although his single occupancy vehicle cost $1 million, he intends for the journey to communicate to the public the viability of solar energy for automobiles [source: CBC].

If that astronomical price stands out to you, consider the projected cost of the forthcoming Venturi Eclectic. The French company plans to show its final version of the model in October 2008, and it's slated for a price point of around $30,000. While that's a far cry from da Luz's expense, considering the size and limited range, this goes to show that solar technology is not cheap.

The cost of solar cells can range from $10 up to $400 each [source: Barry]. The more expensive they become, the better they are at capturing and converting sunlight. Race-worthy solar cars that can travel beyond 60 miles per hour (96 kph) and go for hundreds of miles use thousands of those solar cells across the body of the car. They also cost hundred of thousands of dollars.

Achieving speeds of 60 miles per hour solely from the sun has a lot to do with the weight and aerodynamics of the solar racecars. Their design, combined with the efficiency of the motor allows them to zip down the road with the same oomph that powers a hairdryer [source: MIT Solar Car Team]. While gasoline engine cars direct around 15 percent of the energy from burning fuel to actually moving the car, solar power achieves beyond 90 percent efficiency [source: FuelEconomy.gov].

All this fuel thrift doesn't translate to desirable aesthetics, however. For one thing, these one-seaters look like pancakes on wheels. And as you can guess, driving a car covered in solar panels may not be the most temperate experience. These purely solar-powered cars can heat up quickly since the passenger area is enveloped by the cells.

Then there's the problem of how to get around at night or on rainy days when the sun is nowhere to be seen. Here's where a battery or small gas engine would come in. Most viable solar car projects rely on additional power sources to ensure that the car gets going any time you need it to. In fact, James Dyson of vacuum cleaner fame recently publicized his intention to develop an electric car with a solar roof that would improve the mileage it could get [source: Derbyshire]. Used this way, solar power could serve as a range extender for electric cars, allowing the panels to provide the fuel while the sunlight is abundant, but kicking it to the battery once it goes down.

For related information on future cars, visit the links on the next page.

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Solar Car Competitions

Solar cars haven't caught on with the public yet, but solar car racing has been going on since the 1980s. Common entrants include school, corporate and hobbyist teams. You'll also notice many big-name automakers as team sponsors as well. Here are a couple of the longest-distance examples:

World Solar Challenge: started in 1983, this 1,872-mile (3,012-kilometer) race goes across Australia and happens every three years.

Barry, Courtney. "Here They Come, as Fast as the Sun Will Carry Them." The New York Times. Oct. 22, 2003. (June 27, 2008) http://query.nytimes.com/gst/fullpage.html?res=940CE5D7143FF931A15753C1A9659C8B63